1. Field of the Invention
The present invention relates to a display apparatus including organic electroluminescent (hereinafter referred to as “organic EL”) elements, and more particularly relates to a sealing structure.
2. Description of the Related Art
In recent years, organic EL display apparatuses which are self-luminous have been receiving attention as flat panel displays. In an area (display area) where an image is displayed in an organic EL display apparatus, a plurality of organic EL display elements, each having an organic layer sandwiched between first and second electrodes, are arranged, and the organic EL elements serve as pixels and emit light to display an image. The organic EL elements are highly susceptible to moisture and oxygen. When moisture or oxygen infiltrates into organic EL elements from the outside, the organic EL elements may degrade, resulting in generation of non-light-emitting portions referred to as dark spots.
As a structure for preventing moisture and oxygen from infiltrating into organic EL elements from the outside, Japanese Patent Laid-Open No. 2003-282240 (Patent Document 1) discloses a structure in which a protective film composed of a resin protective film 109 and an inorganic protective film 110 covers organic EL elements, as shown in FIG. 6. According to Patent Document 1, the resin protective film 109 covers the organic EL elements and a surface of the substrate around the organic EL elements, and the inorganic protective film 110 covers the resin protective film 109, an edge thereof, and a surface of the substrate around the resin protective film 109. In such a structure, since the resin protective film 109 which can be an infiltration path of moisture is not exposed to the outside, infiltration of moisture can be prevented, and the organic EL elements can be prevented from being degraded.
Furthermore, in a top-emission-type organic EL display apparatus, a planarizing film 104 composed of a resin material is provided in order to planarize irregularities of pixel circuits 102 disposed between the substrate and the organic EL elements so that layers to be stacked can be prevented from being disconnected (refer to FIG. 7). Since the planarizing film 104 also has the function of protecting the pixel circuits 102 and peripheral circuits 103, the planarizing film 104 is also formed on the peripheral circuits 103 continuously from the display area. When a glass substrate 701 and an organic EL display apparatus having such a structure are sealed with an adhesive 702, moisture may infiltrate from the outside through the planarizing film 104 into the display area, resulting in degradation of the organic EL elements.
In order to solve such a problem, Japanese Patent Laid-Open No. 2005-164818 (Patent Document 2) discloses a technique in which a region B which divides the planarizing film 104 is disposed around the periphery of the display area so as to prevent infiltration of moisture, as shown in FIG. 7.
The structure in which, in order to prevent moisture from infiltrating into organic EL elements, a resin protective film and an inorganic protective film are disposed to protect the organic EL elements is suitable for mass production because production cost and the number of steps can be reduced. However, when such protective films are used in a top-emission-type organic EL display apparatus having a planarizing film disposed substantially over the entire surface of the substrate, in the structure according to Patent Document 1, moisture infiltrates from the outside through the planarizing film into the organic EL elements.
Even in the case where a dividing region is provided in the planarizing film as in Patent Document 2, if an end of the resin protective film 109 is located on the planarizing film 104 outside the dividing region B as shown in FIG. 8, moisture entering from the planarizing film 104 infiltrates through the resin protective film 109 into the display area.
Therefore, in the structure described above, it is very difficult to obtain sufficient reliability in the luminous characteristics of the organic EL elements.